Welcome to the Canon Forums and thanks for your post!
To have a better understanding of your issue, please let everyone know what operating system (Windows Vista/7/8 or Mac OS 10.X) you are using and if you are connected via USB or WI-FI. That way, the community will be able to assist you with suggestions appropriate for your product.
Any other details you'd like to give will only help the Community better understand your issue!
If this is a time-sensitive matter, our US-based technical support team is standing by, ready to help 24/7 via Email at http://bit.ly/Canon-Support or by phone at 1-800-OK-CANON (1-800-652-2666) weekdays between 10 AM and 10 PM ET (7 AM to 7 PM PT).